Manifest destiny was the idea that the nation was meant to spread to the pacific. Latecomers to the midwest set there eyes on california and oregon even though other nations had claimed parts of the land. The U.S. and Great Britain agreed in 1818 to occupy the oregon land jointly. British dominated the region until about 1840. California was a frontier province of Mexico because few Mexicans wanted to live in California although the local government welcomed foreign settlers. Around 1845 more than 700 Americans lived in the state of California. bye the 1840's, there were several east-to-west routes that had been carved, such as the Oregon Trail, the California Trail, and the Santa Fe Trail. As overland traffic increased , the Plains Indians came to resent the threat that posed their way of life. they were afraid that the buffalo herds that relied for on food, shelter, clothing, and tools would soon die off or migrate elsewhere. In 1851, the government negotiated the Treaty of for Laramie to ensure peace. eight Plains Indian groups agreed to very specific geographic boundaries while some territories would belong to the Native Americans forever.